High frequency coaxial switch employing strip-line techniques



Dec. 17, 1963 G. w. WEDEMEYER 3,114,887

HIGH FREQUENCY COAXIAL SWITCH EMPLOYING STRIP-LINE TECHNIQUES Filed May 4. 1959 7 4 40 4 Imm {:34 1.3 4

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United States Patent ()fiice 3,114,887 Patented Dec. 17, 1963 3,114,887 HEGH FREQUENCY KIOAXHAL EiWiTCH EMPLQY- ENG STRIP-LINE TECHWEQUEE George W. Wedemeyer, Los Angeles, Calif., assigncr to Microdot Inc, South Pasadena, Calif, a corporation of California Filed May 4, 1959, Ser. No. 810,331 8 Claims. (Cl. 333-7) The present invention relates generally to coaxial cable switching devices, and is more particularly concerned with switches of the above character, wherein strip-line techniques of switching may be embodied in miniature switches for use with coaxial cables.

In the propagation of high frequency electrical signals, it is often desirable to switch the signals between two or more circuits with a minimum of power reflection towards the generating source as a result of the insertion of the switch into the circuitry. Under such conditions, there are three basic sources of electrical discontinuity, and consequent large reflections, namely:

(1) Abrupt changes in the physical size of the transmission line,

(2) Changes in the propagating mode, and

(3) Changes in the direction of propagation.

Having the above problems and difficulties in mind, it is an object of the present invention to provide a coaxial switch in which adverse electrical effects will, due to the above causes, be reduced to a minimum. In the present invention the above diliiculties are overcome by utilizing an arrangement of strip-line switching elements of a configuration such that the coaxial transverse electro magnetic (TEM) propagation mode will be maintained through the switch.

A further object is to provide improved means whereby signals may be switched with low reflections over a large frequency band width, and with a minimum of cross talk between the operating and unoperating connectors.

Still another object is to provide a strip-line coaxial switch of simple design, and which may be constructed in a manner conducive to ease of manufacture and assembly in quantity, and which will have uniform operating characteristics.

Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.

Referring to the accompanying drawings, which are for illustrative purposes only:

16. l is a plan view of a coaxial switch embodying the features of the present invention, portions of the casing being cut away to disclose the construction and cooperative relationship of internal parts thereof;

FIG. 2 is a front elevational view of the switch, a portion of the forward wall of the casing being cut away to disclose par-ts within the casing;

FIG. 3 is a transverse sectional view taken substantially on line 3-3 of FIG. 1;

FIG. 4 is a detail view showing the construction of the plates of insulating material and the associated stripline conductor carried thereby;

FIG. 5 is an enlarged fragmentary sectional view of the same taken substantially on line 5-5 of FIG. 4; and

FIG. 6 is a view diagrammatically illustrating a modified arrangement of the ground plate.

Referring generally to the drawings, for illustrative purposes, the present invention is shown as comprising a switching device for selectively connecting a common coaxial cable with one or the other of a pair of branch coaxial cables. While this arrangement has been chosen for clarity of illustration, it will be appreciated that the features of construction which are to be subsequently disclosed may be incorporated in coaxial switching devices susceptible of other combinations of coaxial cable switching.

As shown in FIG. 1, the switch of the present invention embodies a housing or casing 10 of two-part construction, being composed of a hollow box-like rectangular member 11 which is open on its back side and arranged to be closed by a back closure 12. The back closure is provided with a peripheral flange 13 arranged to seat against a sealing gasket 14, the closure being retained by conventional means such as securing screws 15.

On the opposite side of the housing from the back closure, that is, on a front wall 16 are mounted a plurality of conventional coaxial jack connectors 17, 18 and 19, these connectors being horizontally aligned and in spaced apart relation. In the embodiment shown, the centermost connector 17 for purposes of discussion may be considered as a common input, while the connectors 18 and 19 may be regarded as connectors for coupling coaxial branch cables to the switch. The switching components will therefore be considered subsequently as arranged for selectively connecting the central connector with one or the other of the branch connectors 18 and 19.

More specifically, as shown in FIG. 31, the jack connector comprises a tubular ferrule 20 having a threaded end 21 which extends through a wall opening of the casing and projects forwardly to the exterior of the casing. The ferrule is secured in mounted position by means of a nut 22 which coacts with a U-shaped bracket 23 formed on the innermost end of the ferrule to provide spaced upper and lower arms 24 and 25 respectively.

The tubular ferrule 20 is arranged to connect with the outermost conducting sheath of the coaxial cable which is connected to the connector and is in electrical connection with the arms 24 and 25 which carry a first set of contacts in the form of spring contact strips 26 and 27 respectively, these contact strips being secured to the associated arms of the bracket by appropriate screws 28. Insulatingly supported in each ferrule is a contact 29 for connection with the center conductor of the associated coaxial cable, this contact terminating within the casing in a second contact 3d of spring finger construction.

Switching is accomplished by means of a movable sandwich structure 31 supported for rectilinear movement in opposite directions. More specifically, the sandwich structure comprises an elongate frame bar 32 of conducting material such as brass, this bar having upturned ends 33 and 34 between which are mounted a pair of plates 35 and 36 which are retained in position by securing screws 37, a spacer 38 serving to hold the plates in spaced apart relation. The plates, as shown in FIG. 3 are supported with one set of corresponding lateral edges positioned be tween the arms of the U-shaped brackets 23 of the connectors, while the other set of corresponding edges extend into a horizontally extending groove as on the inner face of the back closure 12. The rectilinear movement of the sandwich structure is guided by means of pusher rods 40 and 41 which project through end openings of the casing and provide in addition means for manually actuating the switch. It is to be noted, however, that while manual operation is shown for clarity of illustration, the switch may be arranged for actuation by means of linear solenoid or other electromagnetic actuating device.

The plates 35 and 36 are constructed with outer conducting surfaces 4-2 in each case of copper or other suitable material which provide spaced ground surfaces engaged respectively by the spring contacts 26 and 27. The inner surfaces of the plates carry U-shaped strip-line conductors 43 which are in vertical registration and have their ends brought out to the side of the sandwich structure 3,1 laser for engagement with the inner conductor contacts 30 respectively of adjacently disposed connectors. Where the ground surfaces 42 extend the full length of the plates 35 and 36, movement of the sandwich structure switches only the center conductors to interconnect the common coaxial cable with a branch cable, thus leaving the outer conductors of all the cables continuously connected with the ground surfaces.

The utilization of the sandwich structure described above and the insulated strip-line conductors 43 in the manner disclosed permits the strip-line conductor being properly designed to obtain the advantageous operating characteristics of low voltage standing wave ratios (VSWR), low crosstalk, and an arrangement which is relatively insensitive to frequency changes and provides a uniform dielectric material between the plates 35 and 36 and defines a uniform dielectric configuration between the plates. The coaxial transverse electro-magnetic (TEM) propagation mode is maintained through the switching device.

By moving both the strip-line ground surfaces and center conductor in unison, while holding the coaxial connector parts stationary, requires a minimum of mechanical tolerances to be incorporated into the device. This feature enables the incorporation and embodiment of the invention as described above into miniature coaxial switches. The rectilinear movement of the sandwich structure is limited at the operative positions of the switch by abutment of the ends of the plates 35 and 36 against end wall surfaces 44 and 45 of the casing.

There may be operating conditions in which it may be desirable to utilize isolated ground connections when connecting the common cable to each of the branch cables. The switching device of the present invention is readily modified for such operation. Instead of extending the outer surface 42 the full length of the plates 35 and 36, the outer surface may be shortened as shown in FIG. 6 and indicated by the numeral 42. In this arrangement, the ends of the conducting surface are carried slightly past the arms of the strip-line conductor 43, as shown. The contacts 26 and 27 of the respective connectors 17, 18 and 19 will in this arrangement be selectively switched simultaneously with the switching of the central conductor contacts 30.

Various modifications may suggest themselves to those skilled in the art without departing from the spirit of my invention, and, hence, I do not wish to be restricted to the specific form shown or uses mentioned, except to the extent indicated in the appended claims.

I claim:

1. In combination for use with transmission lines having inner and outer conductors to transmit electrical energy at high frequencies, a first conducting member having first and second linear portions and having a third portion extending in a first direction between the first and second portions in a curve defining an arc at every position along the third portion, the conducting member being movable between first and second positions in the first direction and being electrically connected to the inner conductors of the transmission lines in at least one of the first and second positions, a second conducting member connected to the outer conductors of the transmission lines in at least one of the first and second positions of the first conducting member and disposed in the first direction in uniformly spaced relationship to the first, second and third portions of the first conducting members and provided with a length in the particular direction at least as great as the combined lengths of the first, second and third portions of the first conducting member in the first direction and being disposed in overlapping relationship in the first direction to the first and second portions of the first conducting member in both the first and second positions of the first conducting member, means disposed between the first and second conducting members to provide a uniform dielectric configuration between the first and sec i ond members in the first and second positions of the first conducting member, and means operatively coupled to the first conducting member for providing a movement of the first conducting member in the first direction bet een the first and second positions.

2. in combination for use with transmission lines having inner and outer conductors to transmit electrical energy at high frequencies: first and second planar means disposed in spaced relationship in a first direction and having a planar configuration in a second direction transverse to the first direction and constructed to define first and second references of electrical potential on first particular surfaces of the first and second planar means, a pair of electrical conducting members disposed between the first and second planar means in spaced andsymmetrical relationship to the first and second planar means in the first direction and within the space defined by the first and second planar means to define a uniform dielectric configuration between the first and second planar means and the pair of electrical conducting members to define with respective ones of the first and second planar means a pair of half strip lines, each of the electrical conducting members in the pair extending in the second direction, the pair of electrical conducting members being movable in the second direction between first and second positions and being disposed within the space defined by the first and second planar means in the first and second positions of the electrical conducting members, the first particular surfaces of the planar means being electrically connected to the outer conductors of the transmission lines in at least one of the first and second positions of the electrical conducting members and the pair of electrical conducting members being electrically connected to the inner conductors of the transmission lines in at least one of the first and second positions of the electrical conducting members, and means operatively coupled to the pair of electrical conducting members for providing a movement of the electrical conducting members in the second direction between the first and second positions.

3. In combination for use with transmission lines having inner and outer conductors to transmit electrical energy at high frequencies, a first conducting member having first and second portions disposed in spaced and parallel relationship and separated from each other in a first direction and electrically communicating with each other in the first direction through a third portion having a curved configuration, the first conducting member being movable in the first direction between first and second positions, a second conducting member extending in the first direction and disposed in a substantially uniformly spaced relationship to the first conducting member and connected to the outer conductors of the transmission lines in at least one of the first and second positions of the first conducting member, an insulating member disposed between the first and second conducting members at every position between the second conducting member and the first, second and third portions of the first conducting member in the first and second positions of the first conducting member to provide a substantially uniform dielectric field between the first and second conducting members in the first and second positions of the first conducting member, and means operatively coupled to the first conducting member for providing a movement of the first conducting member in the first direction between the first and second positions.

4. The combination set forth in claim 3 in which the insulating member is physically coupled to the first and second conducting members to obtain a simultaneous movement of the first and second conducting memb in the first direction between the first and second positions and in which the second conducting member is provided with a length and disposition relative to the first conducting member to overlap the first conducting member in the first direction.

5. In combination for use with transmission lines having inner and outer conductors to transmit electrical energy at high frequencies, a first conducting member having a flat configuration in a first direction and having a thin dimension in a second direction substantially perpendicular to the first direction and having first and second portions spaced from each other in the first direction and having a third portion of arcuate configuration joining the first and second portions, the first conducting member being movable in the first direction between first and second positions and being disposed relative to the inner conductors of the transmission lines to provide an electrical communication with the inner conductors of the transmission lines in at least one of the first and second positions, a second conducting member having a flat configuration in the first direction and disposed in a substantially spaced relationship to the first conducting member to provide a substantially uniform dielectric material between the first and second conducting members, and an insulating member disposed between the first and second conducting members to provide a dielectric field between the members.

6. The combination set forth in claim 5 in which the first conducting member is disposed against a first surface of the insulating member in substantially flush relationship with the first surface of the insulating member at every position of the first conducting member and in which the second conducting member is disposed against a second surface of the insulating member opposite to the first surface of the insulating member and in substantially flush relationship with the second surface of the insulating member.

7. In combination for use with transmission lines having inner and outer conductors to transmit electrical energy at high frequencies, first and second conducting members disposed in substantially parallel relationship in a first direction and separated from each other by a substantially uniform distance in a second direction substantially perpendicular to the first direction and movable in the first direction between first and second positions and connected in at least one of the first and second positions to the inner conductors of the transmission lines, third and fourth conducting members disposed in substantially parallel relationship to the first and second conducting members and having lengths greater than the first and second conducting members and disposed in overlapping relationship to the first and second members in the first direction and in symmetrical relationship to the first and second conducting members in a second direc tion substantially perpendicular to the first direction to provide a substantially uniform dielectric material between the first and third conducting members and between the second and fourth conducting members and to respectively form a pair of half strip-line conductors with the first and second conducting members, the third and fourth conducting members being connected to the outer conductors of the transmission lines in at least one of the first and second positions of the first and second conducting members, and means operatively coupled to the first and second conducting members for providing a movement of the first and second conducting members between the first and second positions in the first direction.

8. The combination set forth in claim 7 in which insulating means are disposed between the first and third conducting members and between the second and fourth conducting members and are provided with lengths greater than the lengths of the first and second conducting members in the first direction to provide a uniform dielectric field between the first and third conducting members and between the second and fourth conducting members at every position along the first and second conducting members in the first direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,432,476 Hesse Dec. 9, 1947 2,475,647 Spriggs July 12, 1949 2,508,479 Wheeler May 23, 1950 2,759,152 Charles Aug. 14, 1956 2,773,242 Grieg Dec. 4, 1956 2,784,379 Schumemann Mar. 5, 1957 2,825,878 Coleman Mar. 4, 1958 2,926,317 Blitz "Feb. 23, 1960 2,946,024 Mills July 19, 1960 FOREIGN PATENTS 1,065,478 France Oct. 7, 1957 

1. IN COMBINATION FOR USE WITH TRANSMISSION LINES HAVING INNER AND OUTER CONDUCTORS TO TRANSMIT ELECTRICAL ENERGY AT HIGH FREQUENCIES, A FIRST CONDUCTING MEMBER HAVING FIRST AND SECOND LINEAR PORTIONS AND HAVING A THIRD PORTION EXTENDING IN A FIRST DIRECTION BETWEEN THE FIRST AND SECOND PORTIONS IN A CURVE DEFINING AN ARC AT EVERY POSITION ALONG THE THIRD PORTION, THE CONDUCTING MEMBER BEING MOVABLE BETWEEN FIRST AND SECOND POSITIONS IN THE FIRST DIRECTION AND BEING ELECTRICALLY CONNECTED TO THE INNER CONDUCTORS OF THE TRANSMISSION LINES IN AT LEAST ONE OF THE FIRST AND SECOND POSITIONS, A SECOND CONDUCTING MEMBER CONNECTED TO THE OUTER CONDUCTORS OF THE TRANSMISSION LINES IN AT LEAST ONE OF THE FIRST AND SECOND POSITIONS OF THE FIRST CONDUCTING MEMBER AND DISPOSED IN THE FIRST DIRECTION IN UNIFORMLY SPACED RELATIONSHIP TO THE FIRST, SECOND AND THIRD PORTIONS OF THE FIRST CONDUCTING MEMBERS AND PROVIDED WITH A LENGTH IN THE PARTICULAR DIRECTION AT LEAST AS GREAT AS THE COMBINED LENGTHS OF THE FIRST, SECOND AND THIRD PORTIONS OF THE FIRST CONDUCTING MEMBER IN THE FIRST DIRECTION AND BEING DISPOSED IN OVERLAPPING RELATIONSHIP IN THE FIRST DIRECTION TO THE FIRST AND SECOND PORTIONS OF THE FIRST CONDUCTING MEMBER IN BOTH THE FIRST AND SECOND POSITIONS OF THE FIRST CONDUCTING MEMBER, MEANS DISPOSED BETWEEN THE FIRST AND SECOND CONDUCTING MEMBERS TO PROVIDE A UNIFORM DIELECTRIC CONFIGURATION BETWEEN THE FIRST AND SECOND MEMBERS IN THE FIRST AND SECOND POSITIONS OF THE FIRST CONDUCTING MEMBER, AND MEANS OPERATIVELY COUPLED TO THE FIRST CONDUCTING MEMBER FOR PROVIDING A MOVEMENT OF THE FIRST CONDUCTING MEMBER IN THE FIRST DIRECTION BETWEEN THE FIRST AND SECOND POSITIONS. 